Neo_007answered grow question 4 years ago It could be that the plants are using the food, or evaporation, or just drinking the water and concentrating the remaining nutes to a higher than intended amount ( that would not be great ), so start by diluting to be safe when its 30% below the initial line roughly.
But, the next step would be to figure out what it was out of those, by dropping a ppm meter into the water.
If you have your target PPM ( or EC ), then you will be able to discern after you top it off whether it has dropped in the nutrient density, and thus discern whether to bump them up to the intended levels.
Make sense?